Surfactants are compounds composed of both hydrophilic and hydrophobic or lipophilic groups. In view of their dual hydrophilic and hydrophobic nature, surfactants tend to concentrate at the interfaces of aqueous mixtures; the hydrophilic part of the surfactant orients itself towards the aqueous phase and the hydrophobic part orients itself away from the aqueous phase. Due to these properties, surfactants can be used as emulsifiers for emulsion polymerization reactions during the manufacture of paints, Surfactants, in addition, improve wetting of the substrate by the coating, and wetting of the pigment by the resin. The presence of a surfactant can also affect the mechanical, chemical, freezing, and storage stability of the polymers in paints and emulsions. Additionally, surfactants may also affect the water, moisture, heat resistance, and adhesiveness of a polymer film. As such, both ionic and non-ionic surfactants may be used in coating compositions.
Gemini surfactants (sometimes referred to as dimeric surfactants) are a new class of surfactants that have two or more hydrophilic groups and two or more hydrophobic groups in the molecules. Typically, gemini surfactants have low critical micelle concentrations, and may be used in lower amounts than conventional surfactants. Gemini surfactants can be ten to a thousand times more surface-active than conventional surfactants with similar but single, hydrophilic and hydrophobic groups in the molecules. Further, gemini surfactants may be anionic, cationic, nonionic or zwitterionic.
In paint industry, leaching of surfactants, breaking down of emulsion system, and freezing represent major problems in terms of maintaining the quality and durability of the paint. These problems can be overcome by developing new and efficient class of surfactants that are polymeric and self-emulsifying.